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Laboratorial radiative shocks with multiple parameters and first quantifying verifications to core-collapse supernovae

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arXiv 2024年

作者： Zhang, Lu Zheng, Jianhua Yang, Zhenghua Song, Tianming Zhang, Shuai Liu, Tong Wei, Yunfeng Kuang, Longyu Jing, Longfei Lin, Zhiwei Li, Liling Li, Hang Zheng, Jinhua Yang, Pin Zhang, Yuxue Zhang, Zhiyu Zhao, Yang He, Zhibing Li, Ping Yang, Dong Yang, Jiamin Zhao, Zongqing Ding, Yongkun Research Center of Laser Fusion China Academy of Engineering Physics Mianyang621900 China Department of Astronomy Xiamen University Fujian Xiamen361005 China Institute of Applied Physics and Computational Mathematics Beijing100088 China

We present experiments to reproduce the characteristics of core-collapsesupernovae with different stellar masses and initial explosion energies in thelaboratory. In the experiments, shocks are driven in 1.2 atm and 1.9 atm xenongas by laser with energy from 1600J to 2800J on the SGIII prototype laserfacility. The average shock velocities and shocked densities are obtained fromexperiments. Experimental results reveal that higher laser energy and lower Xegas density led to higher shock velocity, and lower Xe gas initial density hasa higher compression. Modeling of the experiments using the 2D radiationhydrodynamic codes Icefire shows excellent agreement with the experimentalresults and gives the temperature. These results will contribute to time-domainastrophysical systems, such as gravitational supernovae, where a strongradiative shock propagates outward from the center of the star after the corecollapses. © 2024, CC0.

关键词： Supernovae

Two-Level preconditioning method for solving saddle point systems in contact computation

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arXiv 2024年

作者： Duan, Xiaoyu An, Hengbin Institute of Applied Physics and Computational Mathematics Beijing100094 China Graduate School of China Academy of Engineering Physics Beijing100088 China CAEP Software Center for High Performance Numerical Simulation Beijing100088 China

In contact mechanics computation, the constraint conditions on the contact surfaces are typically enforced by the Lagrange multiplier method, resulting in a saddle point system. Given that the saddle point matrix is indefinite, solving these systems presents significant challenges. For a two-dimensional tied contact problem, an efficient two-level preconditioning method is developed. This method utilizes physical quantities for coarsening, introducing two types of interpolation operators and corresponding smoothing algorithms. Additionally, the constructed coarse grid operator exhibits symmetry and positive definiteness, adequately reflecting the contact constraints. Numerical results show the effectiveness of the method. Copyright © 2024, The Authors. All rights reserved.

关键词： Lagrange multipliers

Deuteration removes quantum dipolar defects from KDP crystals

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arXiv 2024年

作者： Yang, Bingjia Xie, Pinchen Car, Roberto Department of Chemistry Princeton University PrincetonNJ08544 United States Program in Applied and Computational Mathematics Princeton University PrincetonNJ08544 United States Department of Chemistry Department of Physics Program in Applied and Computational Mathematics Princeton Materials Institute Princeton University PrincetonNJ08544 United States

The structural, dielectric, and thermodynamic properties of the hydrogen-bonded ferroelectric crystal potassium dihydrogen phosphate (KH2PO4), KDP for short, differ significantly from those of DKDP (KD2PO4) [1, 2]. It is well established that deuteration affects the interplay of hydrogen-bond switches and heavy ion displacements that underlie the emergence of macroscopic polarization, but a detailed microscopic model is missing [3, 4]. Here we show that all-atom path integral molecular dynamics simulations can predict the isotope effects, revealing the microscopic mechanism that differentiates KDP and DKDP. Proton tunneling in the hydrogen bonds generates phosphate configurations that do not contribute to the polarization. These dipolar defects are always present in KDP, but disappear at low temperatures in DKDP, which behaves more classically. Quantum disorder confers residual entropy to ferroelectric KDP, explaining its lower spontaneous polarization and transition entropy relative to DKDP. Tunneling should also contribute to the anomalous heat capacity observed in KDP near absolute zero [5, 6]. The prominent role of quantum fluctuations in KDP is related to the unusual strength of the hydrogen bonds in this system and should be equally important in the other crystals of the KDP family, which exhibit similar isotope effects [7]. © 2024, CC BY.

关键词： Hydrogen bonds

The linear response theory approach to the sub-GeV dark matter in the Sun

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arXiv 2023年

作者： Liang, Zheng-Liang Zhang, Ping College of Mathematics and Physics Beijing University of Chemical Technology Beijing100029 China School of Physics and Physical Engineering Qufu Normal University Qufu273165 China Institute of Applied Physics and Computational Mathematics Beijing100088 China

In recent years, the importance of the electronic in-medium effect in the sub-GeV dark matter (DM) direct detection has been recognized and a coherent formulation of the DM-electron scattering based on the linear response theory has been well established in the literature. In this paper, we apply the formulation to the scattering between DM particles and solar medium, and it is found that the dynamic structure factor inherently incorporate the particle-particle scattering and inmedium effect. Using this tool and taking a benchmark model as an example, we demonstrate how the in-medium effect affects the scattering of DM particles in the Sun, in both the heavy and the light mediator limit. Formulae derived in this work lay the foundation for accurately calculating the spectra of solar-accelerated DM particles, which is of particular importance for the detection of DM particles via plasmon in semiconductor targets. Copyright © 2023, The Authors. All rights reserved.

关键词： Electron scattering

Ab Initio Study of Single-and Double-Electron Capture Processes in Collisions of He^(2+) Ions and Ne Atoms

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Chinese physics Letters 2021年第11期38卷 30-36页

作者： Xiao-Xia Wang Kun Wang Yi-Geng Peng Chun-Hua Liu Ling Liu Yong Wu Heinz-Peter Liebermann Robert JBuenker Yi-Zhi Qu College of Material Sciences and Optoelectronic Technology University of Chinese Academy of SciencesBeijing 100049China Institute of Environmental Science Shanxi UniversityTaiyuan 030006China Department of Applied Physics Nanjing University of Science and TechnologyNanjing 210094China School of Physics Southeast UniversityNanjing 210094China Data Center for High Energy Density Physics Institute of Applied Physics and Computational MathematicsBeijing 100088China Fachbereich C-Mathematik und Naturwissenschaften Bergische Universitat WuppertalD-42097 WuppertalGermany

The single-and double-electron capture(SEC, DEC) processes of He^(2+) ions colliding with Ne atoms are studied by utilizing the full quantum-mechanical molecular-orbital close-coupling method. Total and state-selective SEC and DEC cross sections are presented in the energy region of 2 eV/u to 20 keV/u. Results show that the dominant reaction channel is Ne^(+)(2s2p^(6) ^(2)S) + He^(+)(1s) in the considered energy region due to strong couplings with the initial state Ne(2s^(2)2p^(6)^(1)S) + He^(2+) around the internuclear distance of 4.6 a.u. In our calculations, the SEC cross sections decrease initially and then increase whereby, the minimum point is around 0.38 keV/u with the increase of collision energies. After considering the effects of the electron translation factor(ETF), the SEC cross sections are increased by 15%–25% nearby the energy region of keV/u and agree better with the available results. The DEC cross sections are smaller than those of SEC because of the larger energy gaps and no strong couplings with the initial state. Due to the Demkov-type couplings between DEC channel Ne^(2+)(2s^(2)2p^(4)^(1)S) + He(1s^(2)) and the dominating SEC channel Ne^(+)(2s2p^(6) ^(2)S) + He^(+)(1s), the DEC cross sections increase with increasing impact energies. Good consistency can also be found between the present DEC and the experimental measurements in the overlapping energy region.

关键词： SEC DEC Ab Initio Study of Single-and Double-Electron Capture Processes in Collisions of He Ions and Ne Atoms

Finite-Difference Least Square Methods for Solving Hamilton-Jacobi Equations Using Neural Networks

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SSRN

SSRN 2024年

作者： Esteve-Yagüe, Carlos Tsai, Richard Massucco, Alex Department of Applied Mathematics and Theoretical Physics University of Cambridge Cambridge United Kingdom Department of Mathematics Oden Institute for Computational Engineering and Sciences The University of Texas at Austin Austin United States Pavia Italy

We present a simple algorithm to approximate the viscosity solution of Hamilton-Jacobi (HJ) equations by means of an artificial deep neural network. The algorithm uses a stochastic gradient descent-based algorithm to minimize the least square principle defined by a monotone, consistent numerical scheme. We analyze the least square principle's critical points and derive conditions that guarantee that any critical point approximates the sought viscosity solution. The use of a deep artificial neural network on a finite difference scheme lifts the restriction of conventional finite difference methods that rely on computing functions on a fixed grid. This feature makes it possible to solve HJ equations posed in higher dimensions where conventional methods are infeasible. We demonstrate the efficacy of our algorithm through numerical studies on various canonical HJ equations across different dimensions, showcasing its potential and versatility. © 2024, The Authors. All rights reserved.

关键词： Finite difference method

Confidence-Interval Construction with Non-I.I.D. Spot-Checking Trials & its Application in Quantum Information

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Confidence-Interval Construction with Non-I.I.D. Spot-Checki...

Optica Quantum 2.0 Conference and Exhibition, Quantum 2.0

作者： Zhang, Yanbao Seshadri, Akshay Knill, Emanuel Quantum Information Science Section Oak Ridge National Laboratory Oak RidgeTN United States Applied and Computational Mathematics Division National Institute of Standards and Technology BoulderCO United States Department of Physics University of Colorado BoulderCO United States Center for Theory of Quantum Matter University of Colorado BoulderCO United States

ISBN: (纸本)9781957171272

We develop a method to estimate the sum of conditional means of a sequence of random variables given our access to only a subsequence by spot-checking. The method works with non-independent-and-identically-distributed (non-i.i.d.) random variables and can be applied for certifying ongoing quantum information tasks. ©2023TheAuthor(s)

关键词： Energy Information processing Quantum computation Quantum cryptography Quantum information

POINTWISE ESTIMATES FOR THE FUNDAMENTAL SOLUTIONS OF HIGHER ORDER SCHRÖDINGER EQUATIONS WITH FINITE RANK PERTURBATIONS

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arXiv 2025年

作者： Chen, Xinyi Cheng, Han Huang, Shanlin School of Mathematics and Statistics Huazhong University of Science and Technology Hubei Wuhan430074 China Institute of Applied Physics and Computational Mathematics Beijing100088 China Sun Yat-sen University Guangdong Zhuhai519082 China

This paper is dedicated to studying pointwise estimates of the fundamental solution for the higher order Schrödinger equation: i∂tu(x, t) = Hu(x, t), t ∈ R, x ∈ Rn, where the Hamiltonian H is defined as H = (-Δ)m + XN j=1 h , φjiφj, with each φj (1 ≤ j ≤ N) satisfying certain smoothness and decay conditions. We show that for any positive integer m > 1 and spatial dimension n ≥ 1, e-itHPac(H) has an integral kernel K(t, x, y) satisfying the following pointwise estimate: |K(t, x, y)| . |t|- n 2m (1 + |t|- 1 2m |x - y|)- n(m-1) 2m-1 , t , 0, x, y ∈ Rn. This estimate is consistent with the upper bounds in the free case. As an application, we derive Lp-Lq decay estimates for the propagator e-itHPac(H), where the pairs (1/p, 1/q) lie within a quadrilateral region in the plane. © 2025, CC BY.

关键词： Schrodinger equation

Interface-mediated sp2−sp3 interconversion in ultrahard diamond-graphite nanocomposites with supertoughness

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Physical Review B 2024年第13期110卷 134107页

作者： Tengfei Xu Zhaorui Liu Dominik Legut Ruifeng Zhang School of Materials Science and Engineering and Center for Integrated Computational Materials Engineering (International Research Institute for Multidisciplinary Science) and Key Laboratory of High-Temperature Structural Materials and Coatings Technology (Ministry of Industry and Information Technology) IT4Innovations Department of Condensed Matter Physics Faculty of Mathematics and Physics

Recently synthesized diamond-graphite nanocomposites, consisting of diamond and graphite nanodomains interlocked via coherent interfaces (termed gradia), exhibit an impressive combination of ultrahigh hardness and superior toughness [Luo et al., Nature (London) 607, 486 (2022)]. This extraordinary finding challenges the prevailing understanding of the widespread trade-off relationship in strong covalent solids, while the toughening mechanism of gradia remains mysterious. Here, we unveil an sp2−sp3 interconversion mechanism, where the graphitization or the bond failures are effectively suppressed through layer-by-layer migration of the interfaces towards diamond (or graphite) domains, which originates from the sequential metallization starting from the diamond atomic layers adjacent to the interface with weakened sp3 hybridization and the associated inverse process, i.e., metal-semiconductor transition of graphite domain (sp2 to sp3 hybridization). These interface-mediated continuous changes in the localized bonding pattern greatly promote the strain-energy dissipation, leading to a profound tolerance for large strains. Moreover, a size-dependent toughening is demonstrated, attributed to detrimental graphitization and interfacial bond breakage that occur under critically small sp2/sp3 thickness. These findings provide guidance for the experimentally rational design of gradia, and the toughening mechanisms arising from interface-induced electronic structure transition also sheds light on the toughening of other hard but brittle materials through heterophase junctions.

关键词： Chemical bonding Electronic structure Plastic deformation Carbon-based materials Diamond Graphite Solid-solid interfaces First-principles calculations